The present disclosure relates to a system and method for lubricating an engine of a vehicle. More particularly, the present disclosure relates to a system and method for controlling operation of an electronic oil pump to provide improved lubrication of the engine, particularly during cold temperature conditions.
The lubrication system and method in the present disclosure is particularly suited for use with cold weather vehicles such as snowmobiles, but may also be used in other types of vehicles. In conventional lubrication systems, a lubricant such as oil is stored in an oil tank. The oil tank may be integral with or separate from the engine. An oil pump has an input coupled to an output of the oil tank.
Conventional mechanical oil pumps are driven by the engine. In contrast, electric oil pumps are controlled by a signal from an electronic control unit (ECU). In two stroke engines, the oil pump provides oil which is mixed with fuel and burned in the engine. Therefore, it is important for the oil pump to deliver a proper volume of oil to a two stroke engine to maintain the fuel/oil ratio at a desired level.
Vehicles such as snowmobiles are often operated at very cold temperatures. At such low temperatures, the viscosity of the oil in the oil tank and oil pump increases to a high viscosity level. Such high viscosity oil is difficult to pump, especially during initial start up of a cold engine. Both mechanical oil pumps and electric oil pumps are subject to low volumetric flow rates at cold oil temperatures with high oil viscosity. However, unlike a mechanical oil pump which is physically mounted to an engine, an electric oil pump is often remotely mounted on the vehicle. Such remote mounted electric oil pumps are not subject to much pump heating as the engine temperature increases. As such, the electric oil pump control strategy of the present disclosure controls or manipulates an oil pump command signal from the ECU to increase volumetric efficiency of the oil pump such that oil delivery from the oil pump meets the fuel/oil ratio requirements of the engine.
After a cold soak to low ambient temperatures, an electric oil pump volumetric output is lower for the first few oil pump actuations or “shots”. Therefore, the system and method of oil pump output conditioning of the present disclosure eliminates the first few ineffective oil pump shots from an oil volume output calculation so that oil pump efficiency is more stable. This method, used in conjunction with control signal manipulation discussed below, increases oil pump volumetric efficiency without causing an over-oiling condition.
The system and method of the present disclosure manipulates an oil pump command signal drive time such that the drive time is increased with decreasing temperature to increase pump volumetric efficiency of the oil pump. The drive time correction uses both a representative temperature measurement as well as the pump drive frequency which are represented by inlet air temperature and engine speed, respectively. For example, the oil pump characteristic volume is manipulated to account for a reduction in volumetric efficiency of the oil pump at low temperatures even with the increased signal drive time. This allows greater versatility in both low and high frequency pump operation with oils of varying density and kinematic viscosity.
In an illustrated embodiment of the present disclosure, a method is provided for controlling an electric oil pump with a pump control signal generated by an electronic control unit (ECU) of a vehicle. The pump control signal has a variable drive time portion during which the electric oil pump is actuated to supply oil to an engine of the vehicle and a variable cycle time defining a frequency of the pump control signal. The illustrated method includes determining a base pump volume of the electric oil pump; determining a temperature associated with the engine; and correcting the base pump volume using the determined temperature to provide a corrected pump volume. The method also includes determining a speed of the engine; determining a frequency of the pump control signal based on the determined engine speed and the corrected pump volume; determining a drive time of the pump control signal based on the determined engine speed and the determined temperature; and controlling the electric oil pump using a pump control signal having the determined drive time and the determined frequency.
In another illustrated embodiment of the present disclosure, a method is provided of controlling an electric oil pump with a pump control signal generated by an electronic control unit (ECU) of a vehicle. The pump control signal has a variable drive time portion during which the electric oil pump is actuated to supply oil to an engine of the vehicle and a variable cycle time defining a frequency of the pump control signal. The illustrated method includes determining a speed of the engine; determining a volume of oil to deliver from the electric oil pump to the engine based on the determined engine speed; and determining a temperature associated with the engine. The method also includes determining a number of initial ineffective oil pump actuations after start up of the engine due to a high oil viscosity based on the determined temperature; ignoring the determined number of initial ineffective oil pump actuations when determining the volume of oil delivered from the electric oil pump to the engine; determining a frequency of the pump control signal and a drive time of the pump control signal based on the determined temperature and determined engine speed to deliver the determined volume of oil from the electric oil pump to the engine; and controlling the electric oil pump using a pump control signal having the determined drive time and the determined frequency.
Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.
Although the drawings represent embodiments of various features and components according to the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present disclosure.